The present invention relates to a position detecting apparatus of the absolute type, and particularly to a position detecting apparatus such as an optical probe for a 3-dimensional measuring instrument.
A variety of apparatus for the absolute distance measurement by using the light of two sufficiently separate wavelengths have been proposed, such as that disclosed in Japanese Patent Application No. 5-19216 filed by the applicant of the present invention, and any of these apparatus is based on the provision of a plurality of laser sources of different wavelengths for producing the light of two sufficiently separate wavelengths.
However, it has been very difficult for the use of a plurality of laser sources to stabilize each laser source independently. This has necessitated alignment control for the laser sources, making accurate control more difficult.